The present invention relates to an image forming device such as a laser printer.
An image forming device such as a laser printer generally includes a sheet supply section for supplying sheets and an image forming section for forming an image on a sheet supplied from the sheet supply section. The sheet supply section generally includes a sheet supply tray on which a stack of sheets is mounted, a sheet supply roller positioned near one end and above the sheet supply tray, and a separation pad positioned in confrontation therewith. Upon rotation of the sheet supply roller, an uppermost sheet on the sheet supply tray is nipped between the sheet supply roller and the separation pad and is delivered to the image forming section.
The image forming section includes a photosensitive drum, a charger, a scanner device, a developing roller and an image transfer roller those positioned around the photosensitive drum and in order in a rotating direction thereof. In accordance with the rotation of the photosensitive drum, a surface of the photosensitive drum is uniformly charged by the charger, and then, the surface is exposed to laser beam emitted from the scanner device and scanned at high speed in accordance with image data to form an electrostatic latent image on the surface. Then, toners carried on the developing roller are supplied to the surface of the photosensitive drum by the rotation of the developing roller to form a visible toner image on the surface of the photosensitive drum corresponding to the electrostatic latent image. The toner image carried on the surface of the photosensitive drum is then transferred onto the sheet supplied from the sheet supply section when the sheet passes between the photosensitive drum and the image transfer roller. Thus, a toner image can be formed on the sheet.
In the image forming device, paper dusts may be inevitably generated on the sheet due to the friction against the separation pad because each sheet is supplied while being nipped between the sheet supply roller and the separation pad. Thus, image quality may be lowered, if such paper dusts are mixed with the toners at the image forming section.
To avoid this problem, known is a paper dust removing roller disposed upstream of the sheet supply roller. The paper dust removing roller has a width approximately the same as that of the separation pad in order to remove the paper dust on the sheet before the sheet reaches the image forming section. However, paper dusts have already inherently existed over the entire surface of the sheet due to sheet cutting. Therefore, it would be difficult to remove the inherent paper dusts only by such paper dust removing roller having the width the same as that of the separation pad.
Both inherently generated paper dusts as well as the paper dusts generated due to the friction with the separation pad may be removed by a paper dust removing roller as far as the paper dust removing roller has a width the same as the sheet width. However, amount of the paper dust generated by the friction against the separation pad is greater than the inherently generated amount. Therefore, even if the removal of the paper dust is intended by such paper dust removing roller having the paper width, paper dust cannot be removed uniformly, but removal unevenness occurs between an area where paper dusts were generated due to the friction against the separation pad and an area where the paper dusts have been inherently generated. Thus, uniform removal of the paper dusts cannot be achieved.
Further, a plurality of paper dust removing rollers can be provided along a sheet supply path in order to remove the paper dust on the sheet supplied from the sheet supply section. However, a paper dust transport mechanism and a paper dust accumulator are provided for every paper dust removing roller for transporting and accumulating paper dusts removed by each paper dust removing roller. Therefore, an entire structure becomes complicated, and mechanical components and parts are increased, which renders a resultant image forming device bulky and costly.
Therefore, it is an object of the present invention to overcome the above-described drawbacks, and to provide an image forming device capable of efficiently removing paper dust from the sheet and providing high quality image.
Another object of invention is to provide such image forming device with a simplified arrangement and capable of reducing numbers of mechanical parts, yet performing a sufficient paper dust removal by a plurality of paper dust removing units.
Still another object of the present invention is to provide such image forming device capable of stably transporting, by way of the paper dust transport means, the paper dusts removed by the paper dust removing unit to assure a sufficient falling distance between the paper dust removing unit and the paper dust transport means in order to unit and the paper dust transport means in order to provide a sufficient paper dust accumulation space below the paper dust removing unit.
Still another object of the present invention is to provide such image forming device capable of preventing paper dusts absorbed by the paper dust removing unit from again returning back to a sheet transport path in order to avoid mixture of the paper dusts with developing agent such as toners in a image forming operation performed at downstream of the paper dust removing unit.
These and other objects of the present invention will be attained by providing an image forming device for forming an image on an image recording medium, the device including a sheet supply section, an image forming section, a sheet transport path, and an improved at least two paper dust removing units. The sheet supply section includes a sheet supply roller and a separation pad for nippingly supplying each image recording medium therebetween. The image forming section is adapted for forming an image on the image recording medium supplied from the sheet supply section. The sheet transport path extends from the sheet supply section to the image forming section and defines a sheet feeding direction. The at least two paper dust removing units include a first paper dust removing unit and a second paper dust removing unit. The first paper dust removing unit is disposed at a position beside the sheet transport path and is contactable with the image recording medium for removing paper dusts from the image recording medium running in the sheet transport path toward the image forming section. The second paper dust removing unit is disposed at a position beside the sheet transport path and different from the position of the first paper dust removing unit with respect to the sheet feeding direction and also is contactable with the image recording medium for also removing paper dusts from the image recording medium running in the sheet transport path toward the image forming section.
In one preferred embodiment, the first paper dust removing unit includes a first paper dust removing member in contact with the image recording medium during its travel in the sheet transport path, and the second paper dust removing unit includes a second paper dust removing member in contact with the image recording medium during its travel in the sheet transport path. The first paper dust removing member has a width perpendicular to the sheet feeding direction greater than the width of the separation pad, and the second paper dust removing unit has a width perpendicular to the sheet feeding direction greater than the width of the image recording medium. The width of the first paper dust removing member is smaller than the width of the image recording medium. As such, the first paper dust removing member can remove paper dusts from the image recording medium at least in an area corresponding to the width of the separation pad. Also, the second paper dust removing unit can remove paper dusts in overall surface of the image recording medium.
The image forming device further provides a paper dust accumulating section for congregately accumulating therein paper dusts removed by at least two paper dust removing units from the image recording mediums and then released from the respective paper dust removing units.
In other aspect of the invention, there is provided an image forming device including the image forming section, a sheet transport path extending to the image forming section, a paper dust removing member, a scraping member, and a reverse transport preventive member. The paper dust removing member is positioned in confrontation with the sheet transport path and contactable with the image recording medium passing therethrough for removing paper dusts from the image recording medium. The scraping member is in contact with the paper dust removing member for scraping off the paper dusts from the paper dust removing member. The paper dust removing member is supported rotatably in a normal direction equivalent to the sheet feeding direction and a reverse direction opposite to the normal direction. The reverse transport preventive member is disposed between a first contact position defined between the paper dust removing member and the image recording medium and a second contact position defined between the paper dust removing member and the scraping member for preventing the paper dusts released from the scraping member from being transported back toward the sheet transport path during the reverse rotation of the paper dust removing member.
In still another aspect of the invention, there is provided an image forming device including the image forming section, a paper dust removing unit for removing paper dusts from the image recording medium to be supplied to the image forming section, a paper dust transport unit, and a regulation wall. The paper dust transport unit is disposed lower than the first paper dust removing unit for transporting in a paper dust transporting direction the paper dusts falling down from the paper dust removing unit. The regulation wall is disposed at a part of the paper dust transport unit for regulating a flow of the paper dusts.